stream: Return error from ast_stream_topology_set_stream.

ast_stream_topology_set_stream had suppressed error codes from
AST_VECTOR_APPEND.  The result of AST_VECTOR_APPEND needs to be returned
to the caller so they can take appropriate action on the stream.

Change-Id: I6c0d12755743eadba1357f6153526cc055592856

main/stream.c

@@ -415,8 +415,7 @@ int ast_stream_topology_set_stream(struct ast_stream_topology *topology,
 	stream->position = position;
 
 	if (position == AST_VECTOR_SIZE(&topology->streams)) {
-		AST_VECTOR_APPEND(&topology->streams, stream);
-		return 0;
+		return AST_VECTOR_APPEND(&topology->streams, stream);
 	}
 
 	return AST_VECTOR_REPLACE(&topology->streams, position, stream);